Composite turbine buckets



Dec. 6, 1960 D. GERDAN ETAL ,963, 69

COMPOSITE TURBINE BUCKETS Original Filed Jan. 30. 1953 4 Sheets-Sheet 1 I I J 1 I .A i

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INVENTORS ATTORNEYS Dec. 6, 1960 D- GERDAN EI'AL 6 COMPOSITE TURBINE BUCKETS Original Filed Jan. so, 1953 4 Sheets-Sheet 2 INVENTORS BY 07 & e2; P; waw s m ATTORNEYS Dec. 6, 1960 D. GERDAN ETAL 2,963,269

- COMPOSITE TURBINE BUCKETS Original Filed Jan. 30, 1953 1* #7 H 3 I I I 4 Sheets-Sheet 3 ATTORNE Y5 Dec. 6, 1960 D. GERDAN ETAL 2,963,269

COMPOSITE TURBINE BUCKETS Original Filed Jan. 30, 1953 4 Sheets-Sheet 4 YRT W I ATTORNEYS United States Patent COMPOSITE TURBINE BUCKETS Dimitrius Gerdan, Indianapolis, and Stuart Wilder, Jr., Columbus, Ind., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Continuation of application Ser. No. 334,212, Jan. 30, 1953. This application Jan. 5, 1959, Ser. No. 785,092

2 Claims. (Cl. 253-39.-15)

This application is a continuation of our application Serial No. 334,212 filed January 30, 1953, now abandoned.

Our invention relates to fluid directing elements of turbomachines such as are commonly called buckets, vanes, and blades and particularly to improving provision for the cooling of such elements; and to a structure well adapted both for cooling and for manufacture.

Since the limits of performance and efficiency of high temperature machines such as gas turbines are ordinarily imposed by the resistance to temperature of buckets, and vanes, many proposals have been made to cool these elements in one way or another, and many structures have beensuggested providing for circulation of a cooling fluid through or within these fluid directing elements.

In general, these proposals are not without disadvantages of one sort or another: either the dilficulty of manufacture of the element which is to be cooled, or lack of strength of the element, or inefficiency of cooling.

Our invention is directed to a structure for a cooled bucket or vane which is particularly adapted to make eflicient use of the cooling medium and is also particular ly well adapted to manufacturing and fabrication processes now commonly employed in the manufacture of turbine buckets and vanes.

By way of illustration of the principles of the invention, two embodiments thereof in turbine buckets are illustrated and described herein. In brief outline, the buckets according to the invention are formed in two parts, one defining each face of the element, with abutting or confronting inner surfaces united by high temperature brazing or the like. These inner surfaces are ribbed or grooved to provide passages for circulation of a cooling medium and to provide ribs which increase the efficiency of heat transfer between the blade element and the cooling medium flowing therethrough.

The objects of the invention are to improve. the performance of gas turbines and other high temperature turbomachines, to improve the cooling of buckets and the like, and to provide an improved vane or bucket construction particularly adapted for cooling and which may be readily manufactured.

The nature and advantages of the invention and the manner in which the objects are accomplished will be more clearly apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment thereof and the which:

Fig. 1 is a longitudinal sectional view of a turbine bucket according to the first form of the invention shown as mounted in a fragmentary portion of the rim of a turbine wheel;

Fig. 2 is a sectional view of the same taken on the plane indicated by the line 2-2 in Fig. 1;

Fig. 3 is a sectional view of the same takenon the plane indicated by the line 33 in Fig. 1;

Fig. 4 is an end view of the same projected, on the plane indicated by the line 4-4 in Fig. 1;

accompanied drawings, in-

2,963,269 Patented Dec. 6, 1960 Fig. 5. is a sectional view of the same taken onv the plane indicated by the line 5--5 in Fig. 1;

Fig. 6 is a longitudinal sectional view of a second form;

Fig. 7 is a sectional view of the same taken on the plane indicated by the line 7-7 in Fig. 6;

Fig. 8 is a sectional view of the same taken on the plane indicated by the line 88 in Fig. 6;

Fig. 9 is an end view of the same projected on the plane indicated by the line 99 in Fig. 6;

Fig. 10 is a sectional view of the same taken on the plane indicated by the line 10-40 in Fig. 6; and

Fig. 11 is a sectional view of the same taken on the plane indicated by the line 11-11 in Fig. 7.

Referring first to Figs. 1 to 5, these figures show a turbine bucket A of conventional external configuration comprising a blade portion B, a platform portion C at the base of the blade, and a root portion D mounted in a turbine wheel B, only a fragmentary part of which is shown. The platform C and root portion D may be considered as forming the foot of the bucket as distinguished from the blade B. The root part D is formed with serrations 14 of conventional form which engage in mating serrations 16 extending across the rim of the turbine wheel E, this being the well known fir tree mounting. The blade, which is of any suitable configuration and isillustrated as being of a typical twisted airfoil section, extends from the root and is supported thereby.

The bucket consists of two parts 17 and 18 united together. Each of these two parts 17 and 18 defines one of the faces of the blade and the two parts confront or abut each other on a warped surface extending from the leading to the trailing edge of the blade, the surface being identified as 19. The parts 17 and 18 also define the two mating parts which. together form the blade root, the junction surface 19 continuing into the blade root. It will thus be seen that the entire bucket comprises two parts having mating internal surfaces which when joined together form a bucket of conventional external con-' figuration.

By so forming the bucket of two parts it becomes feasible to provide highly adequate cooling arrangements within the bucket. Each of the two parts of the bucket has extending through the blade portion a rather wide groove 22 adjacent to the leading edge, another ratherwide groove 23 adjacent the trailing edge, and a contending v spanwise of the blade.

and 23 and do not reach the tip grooves22. and 23. As will'be apparent, when the two: parts of the bucket are assembled together in abutting: relation these grooves define open-ended passages through. the blade portion extending from adjacent the blade root". and, when the blade is mounted, from adjacent the rim of the turbine wheel E to the tip ofthe blade.

Provision is made in the turbine wheel to admit a cool ing fluid such as air to the root of the bucket and thebucket is formed to deliver this air to the passages in theblade. As will be most clearly apparent from Fig. 1, the= inner end of the bucket root is cut away to define a.-

chamber 31 between the ends of the blade root to which extending?) lengthwise of the bucket through the root through which the air flows to a distributing chamber 34 extending chordwise of the blade across the root and in communication with all of the passages 22, 23,. and 24. This dis tributing chamber 34 is formed similarly to the passage 33 by forming confronting depressions in the mating faces of the bucket parts. As will be apparent, the form of each part is such that it may be quite readily made by casting with no coring problems or reentrant surfaces. Thus, the casting of the individual parts presents no problem more diflicult than the casting of the ordinary solid turbine buckets, which present some problems because of the nature of the materials employed and their peculiar shapes.

When the parts are cast, the mating surfaces may be sufficiently accurate that it will only be necessary to dress them before brazing, or, if not, the mating surfaces can be ground so as to fit accurately. When this has been done, the parts may be suitably prepared with the brazing material and heated in face to face relation to complete a brazed joint over the entire mating surfaces of the blade portion and the root portion. As will be apparent, the two parts are united along the leading and trailing edge of the blade, at the ribs 26, and throughout a considerable part of the root. The serrations in the root for mounting the bucket may be finished in accordance with usual practice. The bucket according to the invention defines coolant passages of sulficiently restricted area that satisfactory air velocity may be obtained without too great flow, the ribs 26 provide a large heat exchange surface, and no blade liner or other additional part to direct flow through the blade is required.

The cooling may be relied upon to make possible higher temperatures in the engine; or, by virtue of the cooling, the blade may operate at lower temperatures with the same gas temperatures as customarily employed with uncooled blades. In this latter case, the advantage of the invention is primarily in utilization of less critical and more easily handled materials for the bucket.

The form of the invention shown in Figs. 6 to 11 differs from that previously described principally in that the bond between the two parts of the bucket is not a direct face to face one; a metal sheet is interposed between the confronting surfaces and bonded to each of the parts so that the metal sheet forms a part of the bond between them. Since the configuration of parts to a large extent is similar in the two forms and parts in the form of Figs. 6 to 11 corresponding to those of Figs. 1 to are identified by the same reference characters with the addition of a prime, it will be necessary only to describe the differences between the two forms. The turbine wheel E is the same in both cases, and the external form of the root likewise. The two blade parts 17' and 18' may be quite similar to those previously described. However, the grooves 22 and 23 of Fig. l are omitted.

Each part of the blade has on its inner surface a number of grooves 24' extending from the base of the blade to the tip, and additional grooves 37 which extend from the root to an intermediate point of the span of the blade. Sandwiched or interposed between the parts 17' and 18' is a sheet 38 which, as will be most clearly apparent from Figs. 9 to 11, extends entirely across the interface of the two parts at the root and in the lower part of the base of the blade. The sheet 38 has a margin, edge, or periphery extending continuously around the boundary thereof. At about the middle of the span of the blade the sheet 38 is cut away from the trailing edge as indicated by the broken lines 38 and 38 in Fig. 6 so that a relatively narrow space or passage 39 is left between the parts 17 and 18' adjacent the trailing edge over the outer part of the span of the blade. The passage 39 is supplied through the grooves 37 and discharges at the free end or tip of the blade. The parts 17 and 18 are brazed to the sheet 38 and are additionally brazed together along the trailing edge as indicated at 41 in Fig.

.9 bY011d the point at which the sheet 38 ceases to extend to the trailing edge of the blade. The arrangement for supplying air to the passages 24' and 37 is similar to that for bringing air into the blade previously described. The part 17 extends downwardly as indicated at 43 to close the ends of the blade groove 16 in the wheel rim. The center part of both sides of the blade root are relieved upwardly as indicated at 44, the principal attachment being at the end of the blade root adjacent the faces of the wheel. A passage 45 extending through the blade root and cast into the inner faces of the parts 17 and 18' carries air from the chamber 31 to the passages 24 and 37 in the blade. The lower end of the sheet 38 is notched or arched, as will be clearly seen at 48 in Figs. 7 and 8, so that the margin of the sheet 38 follows in a general way the margins of the forward, rear, and upper boundaries of the passage 45. The cooling air introduced through the passage 32 flows into the space 31 under the blade root and through the space 45 into the passages 24' and 37 on each side of the sheet 38. The air flowing through passages 37 is discharged at the upper end of these passages into the space 39 between the two parts of the blade, and all of the air ultimately exhausts at the tip of the blade.

The provision of the sheet 38, while it requires another part, is advantageous to some extent in that the sheet fills up the interior of the blade and thus the passages such as 24' for coolant are concentrated nearer the outer surface of the blade. In other words, for a given flow of air, the flow will be more rapid and somewhat more effective cooling will be had.

It will be apparent that buckets according to either form of the invention are advantageous in that they are lighter than conventional solid buckets but, because of the ribbed construction, they are physically strong. Very adequate provision for cooling is effected, and the buckets may be manufactured by application of known casting, brazing, and machining techniques. The invention is extremely flexible in that it is readily adapted to buckets having various root forms and various blade contours. The application of the principles of the invention to a turbine nozzle vane, for instance, will be obvious, since such a vane may be substantially identical to a turbine bucket without the root portion; that is, similar to the blade portion only of a turbine bucket. Such nozzle vanes are ordinarily supported at both ends in shroud rings, and a vane constructed according to the invention could be mounted in shroud rings in any suitable manner.

The description herein of the preferred embodiments of the invention for the purpose of illustrating the principles thereof is not to be considered as limiting the invention, since many modifications of the invention within the scope thereof may be devised by the exercise of skill in the art.

We claim:

1. A turbine bucket or the like comprising a blade having leading and trailing edges and a root configured to engage a turbine wheel and support the bucket thereon, the bucket including two opposed parts, each part extending from the leading edge to the trailing edge of the blade and defining one face of the blade and one portion of the root, the said portion being engageable with the turbine wheel; and a metal sheet interposed between the said parts, the sheet extending into the root and into the blade and extending from the leading edge to the trailing edge of the blade; the said parts having surfaces internal to the bucket in mutually confronting relation, the confronting surfaces of the bucket parts having grooves therein extending spanwise of the blade from the root to the tip of the blade and ribs extending from the parts between the grooves, the grooves defining with the sheet coolant passages and the ribs providing heat transfer surfaces; the said parts being united with opposite faces of the said sheet at the leading and trailing edges of the said parts and along the said ribs; the bucket root defining a coolant entry connected to the said passages.

2. A turbine bucket or the like comprising a blade having leading and trailing edges and a root configured to engage a turbine wheel and support the bucket thereon, the bucket including two opposed parts, each part extending from the leading edge to the trailing edge of the blade and defining one face of the blade and one portion of the root, the said portion being engageable with the turbine wheel; and a metal sheet interposed between the said parts, the sheet having a margin, the sheet extending into the root and into the blade to the tip of the blade and extending from the leading edge to the trailing edge of the blade through only the inner portion of the span of the blade from the root, the margin of the sheet being spaced from the trailing edge of the blade through the outer portion of the span of the blade; the said parts having surfaces internal to the bucket in mutually confronting relation, the confronting surfaces of the bucket parts having grooves therein extending spanwise of the blade from the root to the tip of the blade and ribs extending from the parts between the grooves, the grooves defining with the sheet coolant passages and the ribs providing heat transfer surfaces, the said parts being united with opposite faces of the said sheet at the leading and trailing edges thereof and along the said ribs, the said parts having a space between them through the said outer portion of the span of the blade between the margin of the sheet and the trailing edge and means joining the parts at the trailing edge through the said outer portion thereby defining a passage extending to the tip of the blade connected for flow of coolant with at least one of the firstmentioned passages; the bucket root defining a coolant entry connected to the first-mentioned passages.

References Cited in the file of this patent UNITED STATES PATENTS 2,779,565 Bruckrnan Jan. 29, 1957 

